Liquid dispensing systems are used for applying liquid materials to a substrate or surface. In many applications, the presence of an air bubble can compromise the quality of the liquid bead that is applied. Accordingly, various techniques have been employed to detect bubbles in the liquid material. U.S. Pat. No. 5,182,938 (the “'938” patent hereinafter) describes method and apparatus for detecting bubbles in a liquid dispensing system, the entire disclosure of which is fully incorporated herein by reference.